Regulation And Mechanism Of Hydrophobicity Of Natural Zeolite By Acid Treatment And Organic Modification

The treatment of environmental pollutants is an important subject of national economy and people's livelihood.The treatment of environmental pollutants by porous minerals represented by natural zeolite and its modified minerals is one of the research hotspots at home and abroad.However,natural zeolite with low Si/Al ratio and high content of hydroxyl group has high hydrophilicity,which leads to its poor adsorbability to hydrophobic pollutants,and greatly limits its wide application in environmental pollutant treatment.Although domestic and foreign researchers have proved that acid treatment and organic modification can effectively improve the hydrophobicity of natural zeolites,the relevant research work is still very limited,and there is still a lack of systematic research on the regulation effect and mechanism of acid treatment and organic modification on the hydrophobicity of natural zeolites.Aiming at this problem,this paper has carried out a lot of research work.The main research contents and results are as follows:(1)Nitric acid was used to treat natural zeolite to improve its Si/Al ratio.The better acid treatment condition was determined by orthogonal experiment as 70?:48 h:8 M.The Si/Al ratio of natural zeolite was controlled by controlling the concentration,time and temperature of acid treatment.On this basis,zeolite with SiO2/Al2O3 ratio of 20.0-372.7 was obtained by controlling the concentration of acid treatment.With the increase of Si/Al ratio of zeolite,the specific surface area and pore volume of zeolite were significantly increased,and the content of Si-OH group was increased,while the crystallinity was obviously decreased.Compared with the natural zeolite,the adsorption capacity of high silica zeolite to water vapor decreased by more than 67%,and the hydrophobicity was significantly increased.(2)The modification of natural zeolite by dodecyl trimethoxy silane(DTS)showed that the modification of DTS had little effect on the crystal structure of zeolite.The critical surface tension of zeolite samples was 28.77-64.99 mN/m when the modified DTS was 0.2%-10%.The hydrophobicity of natural zeolite can be controlled quantitatively by controlling the modified amount of DTS.Amino functionalized hydrophobic zeolite was successfully prepared by 3-aminopropyltriethoxysilane(APTMS)modification of natural zeolite,and its critical surface tension was 46.6 mN/m.(3)Zeolite,acid treatment zeolite,DTS and APTMS modified zeolite were used to treat benzene,toluene,kerosene,naphthalene and dichromate ion pollutants respectively.It was found that acid treatment and DTS modification could effectively improve the adsorption effect of zeolite on benzene,toluene and kerosene.The improvement of adsorption of zeolite to benzene and toluene by acid treatment is closely related to the improvement of surface hydrophobicity.The hydrophobicity of DTS modified zeolite was linearly positively correlated with its adsorption to kerosene.APTMS modification significantly improved the adsorption effect of zeolite on naphthalene and dichromate acid ions,which was mainly attributed to the amino functional group and the hydrophobic propyl group on the zeolite surface.